<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.js"></script>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        body{
            height: 2000px;
            background: url(images/fvb.jpg) no-repeat;
        }
    </style>
</head>
<body>
    <script>
        $(window).scroll(function(){
            var scrollTop = $(window).scrollTop()  // 获取滚动条距离顶部的高
            var availHeight = $(window).height() // 获取可视区的高
            var dw = $(document).height()  // 获取内容区域的高
            console.log(dw); 
            /* 滚动条的距离+可视区的高 = 内容区域的高 */
        })
    </script>
</body>
</html>